1. Field of the Invention:
The present invention relates to a magnetic tape recording and reproducing apparatus suitable for use in a data recording and reproducing apparatus called a data streamer.
2. Description of the Related Art:
There have been developed various kinds of recording and reproducing apparatus each of which records digital data on a magnetic tape and reproduces the recorded data by using a magnetic head disposed on a rotary head drum. The recording and reproducing apparatus using the rotary head drum records data such that tracks slanted relative to the longitudinal direction of the magnetic tape are successively formed.
In this case, since it is usually required upon reproduction to effect a tracking control for controlling the magnetic head to accurately trace the tracks formed on the magnetic tape and hence to accurately control a tape travel system, the rotation phase of the rotary head drum and an arrangement of the recording and reproducing apparatus becomes complicated. Moreover, since it is necessary to widen a track width to the extent that the magnetic head can trace the track accurately, this necessity to widen the track width becomes a bar to an increase of the recording density with which data are recorded on the magnetic tape.
In order to solve the above problem, the assignee of this application developed a recording and reproducing apparatus which can reproduce recorded data from a magnetic tape accurately in a so-called non-tracking system in which the tracking control and so on are not required. FIG. 1 shows an arrangement of a rotary head drum 1 of the recording and reproducing apparatus. A magnetic head A.sub.R and a magnetic head B are disposed at predetermined positions adjacent or close to each other on the rotary head drum 1. In this case, the magnetic head A.sub.R and the magnetic head B have azimuth angles which are different from each other. The magnetic head A.sub.R is used only for recording, and the magnetic head B is used for both recording and reproduction. A magnetic head A.sub.P used only for reproduction is disposed on the rotary head drum 1 at a position which is 180.degree. apart from the magnetic head B, i.e., opposite thereto on the same diameter of the rotary head drum 1. An azimuth angle of the magnetic head A.sub.P is set equal to that of the magnetic head A.sub.R used only for recording. A magnetic tape T is wrapped around the rotary head drum 1 and brought in contact therewith for about 100.degree..
A process carried out when the recording and reproducing apparatus records data will be described with reference to FIGS. 2A to 2C and 4. Initially, the magnetic tape T is traveled at a constant speed and the rotary head drum 1 is rotated at a predetermined speed. While the rotary head drum 1 makes a first rotation, as shown in FIG. 2A, the magnetic head A.sub.R scans the magnetic tape T and records data thereon (this recording is represented by a reference symbol Ra in FIG. 2A) to form a slant track Ta of one recording azimuth angle as shown in FIG. 4. While the rotary head drum 1 makes a second rotation, as shown in FIG. 2B, the magnetic head B scans the magnetic tape T and records data thereon (this recording is represented by a reference symbol Rb in FIG. 2B) to form a slant track Tb of the other recording azimuth angle as shown in FIG. 4 at a portion adjacent to the track Ta. Hereinafter, the tracks Ta and Tb are alternately formed during every one rotation of the rotary head drum 1.
In this case, as shown in FIGS. 2A and 2B, while the rotary drum head 1 is rotated and one of the magnetic heads A.sub.R and B records data on the magnetic tape T, the other of the two does not record data thereon. The magnetic head A.sub.P used only for the reproduction is not used during the recording as shown in FIG. 2C.
Subsequently, a process carried out when the recording and reproducing apparatus reproduces data will be described with reference to FIGS. 3A to 3C and 4. Similar to the recording process in this case, the magnetic tape T is traveled at a constant speed and the rotary head drum 1 is rotated at a predetermined speed (which is the same as that used upon the recording). While the rotary head drum 1 makes a first rotation, as shown in FIG. 3B, the magnetic head B scans the magnetic tape T and reproduces data therefrom (this reproduction is represented by a reference symbol Pa in FIG. 3B). After the reproduction Pa is carried out and the rotary head drum 1 is rotated by about 180.degree., as shown in FIG. 3C, the magnetic head A.sub.P scans the magnetic tape T and reproduces data therefrom (this reproduction is represented by a reference symbol Pb in FIG. 3C). Respective loci of the magnetic heads B and A.sub.P produced when they trace the tracks in the reproduction Pa and the reproduction Pb are loci La and Lb not shown in FIG. 4.
While the rotary head drum 1 makes a second rotation, as shown in FIG. 3B, the magnetic head B scans the magnetic tape T and reproduces data therefrom (this reproduction is represented by a reference symbol Pc in FIG. 3B). After the reproduction Pc is carried out and the rotary head drum 1 is rotated by about 180.degree., as shown in FIG. 3C, the magnetic head A.sub.P scans the magnetic tape T and reproduces data therefrom (this reproduction is represented by a reference symbol Pd in FIG. 3C). At this time, not shown in FIG. 4, respective loci Lc, Ld of the magnetic heads B and A.sub.P during the reproduction Pc and the reproduction Pd are displaced from the loci La, Lb by an amount of about one-track width. The magnetic head A.sub.R used only for recording is not used during the reproduction as shown in FIG. 3A. A comparison between the recording process shown in FIGS. 2A to 2C and the reproduction process shown in FIGS. 3A to 3C reveals that in the reproduction process data is reproduced with a density that is twice as high as that of the recording density.
When such reproduction is carried out, a signal reproduced from the track Ta with one recording azimuth angle is obtained in the reproduction Pa and the reproduction Pc carried out by the magnetic head B, and a signal reproduced from the track Tb with the other recording azimuth angle is obtained in the reproduction Pb and the reproduction Pd carried out by the magnetic head A.sub.P. Since the tracking control is not effected during the reproduction in this system, in that the loci of the magnetic heads B and A.sub.P do not correspond to the tracks formed on the magnetic tape T as shown in FIG. 4, it is possible to substantially obtain a complete recording signal of one track Ta by synthesizing the signals obtained by the reproduction Pa and the reproduction Pc. Similarly, it is possible to substantially obtain a complete recording signal of one track Tb by synthesizing the signals obtained by the reproduction Pb and the reproduction Pd.
When data is reproduced with a density that is twice as high as the recording density as described above, it is possible to reproduce recording signals accurately without tracking control. Accordingly, in this non-tracking system, it is possible to set a track width regardless of the tracking control upon the reproduction, and it is possible to realize a high recording density. In the above-mentioned example, although data is reproduced at a density that is twice as high as the recording density, the rotary head drum 1 is rotated at the same constant speed during both the recording and reproduction processes. Therefore, it is possible to simplify an arrangement of a drive system for the rotary head drum 1.
When a signal recorded by the recording and reproducing apparatus of this system is an audio signal, even if a signal obtained by such a reproduction process has a blank portion, a signal at the blank portion is estimated by interpolation to obtain an audio signal sufficient to be used in the reproduction process. However, when data such as a computer program or the like is recorded, it is necessary to completely prevent reproduced signal from having a blank. The above necessity is not satisfied by the recording and reproduction processes of the recording and reproducing apparatus of the above system. Moreover, when data such as a computer program or the like is recorded, it is necessary to record such recording data which is completely free from any blank portion.